<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>addDaysToDate</title>
</head>

<body>
    <div>打开浏览器控制台查看结果</div>
    <script>
        const addDaysToDate = (date, n) => {
            const d = new Date(date);
            d.setDate(d.getDate() + n);
            return d.toISOString().split('T')[0];
        };
        console.log(addDaysToDate('2020-10-15', 10)); // '2020-10-25'
        console.log(addDaysToDate('2020-10-15', -10)); // '2020-10-05'
    </script>
</body>

</html>